U.S. patent application number 12/084804 was filed with the patent office on 2009-11-05 for extruder.
Invention is credited to Josef A. Blach.
Application Number | 20090274003 12/084804 |
Document ID | / |
Family ID | 37575301 |
Filed Date | 2009-11-05 |
United States Patent
Application |
20090274003 |
Kind Code |
A1 |
Blach; Josef A. |
November 5, 2009 |
Extruder
Abstract
In an extruder wherein the slip-on elements (1) have a
cross-sectional profile comprising circular arcs corresponding to
the maximum slip-on element diameter, the slip-on element core
diameter and the center distance of the slip-on elements (1), the
slip-on element (1) has no shaft-to-hub connection in the area of
the circular arc corresponding to the slip-on element core diameter
and/or it is provided at its ends with reinforcement segments (13,
14).
Inventors: |
Blach; Josef A.; (Lauffen,
DE) |
Correspondence
Address: |
FLYNN THIEL BOUTELL & TANIS, P.C.
2026 RAMBLING ROAD
KALAMAZOO
MI
49008-1631
US
|
Family ID: |
37575301 |
Appl. No.: |
12/084804 |
Filed: |
October 12, 2006 |
PCT Filed: |
October 12, 2006 |
PCT NO: |
PCT/EP2006/009847 |
371 Date: |
May 9, 2008 |
Current U.S.
Class: |
366/84 ;
366/300 |
Current CPC
Class: |
B29C 48/03 20190201;
F16D 1/101 20130101; B29C 48/40 20190201; B29C 48/2564
20190201 |
Class at
Publication: |
366/84 ;
366/300 |
International
Class: |
B29C 47/40 20060101
B29C047/40; B01F 7/00 20060101 B01F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2005 |
DE |
10 2005 053 907.6 |
Claims
1. An extruder having at least two axially parallel support shafts
(4) with slip-on elements (1) configured as conveying and/or
working elements slipped thereon antirotationally by a shaft-to-hub
connection, said elements meshing with adjacent shafts (4), whereby
at least some of the slip-on elements (1) have a cross-sectional
profile (2) comprising circular arcs (A-B, E-F and A-E)
corresponding to the maximum slip-on element diameter (D), the
slip-on element core diameter (d) and at most the center distance
(Ax) of the slip-on elements (1), characterized in that the slip-on
element (1) is configured, in the area of the circular arc (E-F)
corresponding to the slip-on element core diameter (d), without
torque transmission of the shaft-to-hub connection with flat or
partly flat contact against the support shaft (4), and two groups
of at least two splines or teeth each are provided for torque
transmission, the distance from group to group being greater than
that from tooth to tooth.
2. The extruder according to claim 1, characterized in that each of
the two groups has at least three teeth.
3. The extruder according to claim 1, characterized in that the
slip-on element (1) lies flat or partly flat against the support
shaft (4) in the form of a circular arc or straight line in the
area without a shaft-to-hub connection.
4. The extruder according to claim 1, characterized in that the
reinforcement segment (8, 9; 13, 14) is of annular
configuration.
5. The extruder according to claim 4, characterized in that the
reinforcement segment is configured as a concentric ring (8, 9) or
as a cam-shaped flaring ring (13, 14).
6. The extruder according to claim 1, characterized in that the
shaft-to-hub connection is an involute, serration or splined shaft
connection.
7. The extruder according to claim 1, characterized in that the
conveying elements are constituted by screw conveyor elements and
the working elements by screw elements with an opposite direction
of thread, kneader blocks, blisters or toothed disks.
8. The extruder according to claim 1, characterized in that a
multi-spline shaft connection which is only partially effective on
the circumference is provided for torque transmission.
9. The extruder according to claim 1, characterized in that the
reinforcement segment (8, 9; 13, 14) is executed with a diameter
that is greater than the slip-on element core diameter (Dk) and
corresponds at most to the center distance (Ax).
Description
[0001] This invention relates to an extruder having at least two
support shafts according to the preamble of claim 1.
[0002] For nonrotatably connecting the support shaft with the
screws or similar slip-on elements, different shaft-to-hub
connections are known.
[0003] Thus, DE-C 813 154 discloses a machine with two shafts
wherein a feather key or a square profile is used as a shaft-to-hub
connection. According to DE 77 01 692 U1 a multiple spline shaft is
used as a shaft-to-hub connection with an integrated spline, while
DE 27 50 767 A1 and EP 0 001 970 A1 describe circular shafts with
three separate sunk keys with the same pitch angle, and EP 0 330
308 A1 two keys with an unequal pitch angle. What is primarily used
nowadays, however, is the involute shaft according to DIN 5480.
[0004] Further, there are described and compared in
"Konstruktionsbucher", Springer-Verlag, 1984, pages 210 and 211, a
variety of form-fitting shaft-to-hub connections with direct and
indirect form closure with consideration of the fatigue notch
factors and fatigue strength fundamental for the design of the
machine. However, the hub has a constant wall thickness in these
cases. In an extruder of the type stated in the preamble of claim 1
wherein the screw elements or similar slip-on elements closely
intermesh on the entire circumference, however, the axial profile
of the slip-on element is determined by three circular arcs
corresponding to the screw outside diameter, the screw core
diameter and the center distance of the shafts (cf. EP 0 002 131
B1).
[0005] The most economical screw shaft is that with the greatest
conveying volume and simultaneously the highest input torque. The
total cross section of a screw conveyor system is limited by the
diameter of the housing bore and the distance between adjacent
housing bores. It must be distributed proportionately over four
cross sections according to the technical requirements and
possibilities as well as the demand. For transporting the product,
the free conveying surface is first defined, which is determined by
the outside diameter of the screw element and the flight depth.
This also defines the core diameter of the screw element and the
center distance relative to the adjacent support shaft. Secondly,
the support shaft requires the calculated usable surface proportion
for axially conducting the required shaft torque for the subsequent
slip-on elements. Thirdly, the constructionally necessary surface
requirement for transferring the proportionate torque for the
slip-on element must be taken into account, and fourthly the
remaining cross-sectional area of the slip-on element in relation
to the support shaft torque for a dependable slip-on element is
left.
[0006] Each support shaft, which generally has a length
corresponding to at least twenty times the housing bore diameter,
has a multiplicity of slip-on elements slipped thereon close
together. The highest possible torque that can be transmitted to
the greatest calculated usable support shaft diameter dTi crucially
determines the economical use of the extruder.
[0007] The efficiency and economy of an extruder is therefore
determined by highest permissible long-term torque at the same time
as highest volume yield of the extruder.
[0008] It is described in "Kunststoffe" 2/2005, page 75, that the
performance limiting machine element of a double-screw extruder is
primarily the screw core diameter. The deeper the screw elements
are cut, i.e. the greater the increase in free volume of the screw
elements is, however, the smaller the remaining cross section for
the screw core diameter and the associated shaft-to-hub connection
will be. The problem is seen here in the tooth root strength of the
DIN or a similar profile, so that an asymmetric toothing is
proposed for better force transmission and stress distribution.
Apart from the elaborate production of the asymmetric toothing, the
performance of this extruder is also increasable further.
[0009] It is the object of the invention to substantially increase
the volume yield of an extruder at equal torque.
[0010] This is achieved according to the invention by the extruder
characterized in claim 1. Advantageous embodiments of the invention
are rendered in the subclaims.
[0011] According to the invention, the flight depth of the
conveying or similar slip-on element is increased at high torque
transmission of the shaft-to-hub connection. That is, at equal
center distance the outside diameter of the slip-on element is
greater and the core diameter of the slip-on element reduced by the
same measure, which considerably increases the free conveying
surface of the conveying element or working surface of the Working
element and thus the performance of the extruder.
[0012] For this purpose, the slip-on element whose cross section
comprises three circular arcs according to the preamble of claim 1
is (1) configured in the area of the circular arc corresponding to
the slip-on element core diameter without a shaft-to-hub connection
with flat contact against the support shaft and/or (2) provided at
its ends with reinforcement segments.
[0013] The slip-on element has the smallest wall thickness in the
area of the circular arc corresponding to the slip-on element core
diameter. When the shaft transmits a torque, said shaft twists more
than the slip-on elements which are harder and torsionally stiffer
than the shaft. The slip-on element therefore absorbs this force in
the particular area of the shaft. Upon this force transmission the
ends at the lowest thickness of the slip-on element are exposed to
the strongest load.
[0014] That is, it is necessary to at least maintain a minimum wall
thickness of the slip-on element in the area of the circular arc
with the slip-on element core diameter.
[0015] This is obtained in the invention by providing no force
transmission of the shaft-to-hub connection in this area. Thus, the
cross-sectional area that the shaft-to-hub connection otherwise
occupies in this area can be added to the cross-sectional area of
the slip-on element in this area and thus the flight depth
accordingly increased without impairing the strength of the support
shaft.
[0016] Since the usable support shaft diameter dTi does not change,
there is no reduction of the transmittable torque.
[0017] A support shaft configured according to the invention can be
produced in a simple manner by removing the toothing of the shaft,
e.g. by grinding, from a conventional support shaft, e.g. an
involute shaft as according to DIN 5480, in the area against which
the slip-on element lies with its thinnest area corresponding to
the circular arc of the slip-on element core diameter.
[0018] The surface with which the support shaft and the slip-on
element fit in the area of the slip-on element with the circular
arc corresponding to the slip-on element core diameter can be a
surface curved in a circular arc, or a plane surface, i.e. one
corresponding in cross section to a straight line.
[0019] Additionally and in the case of single-start slip-on
elements, the slip-on element can be reinforced at its ends by
preferably annular reinforcement segments in order to absorb the
above-described great forces occurring at the ends of the slip-on
element upon torque transmission.
[0020] The product flow is slowed down by the reinforcement
segments, but this effect is partial and so slight that it does not
play any part in practice.
[0021] As calculations and experiments have shown, the inventive
extruder can increase volume yield by about 30% at equal
torque.
[0022] Moreover, the invention increases the sealing surface
preventing material from penetrating between the slip-on elements
and the shaft and cracking there.
[0023] The shaft-to-hub connection in the inventive extruder is
preferably constituted by an involute, serration or splined shaft
connection. Suitable connections have proved to be in particular
ones in which the keyways in the slip-on element and the teeth of
the shaft are of rounded configuration.
[0024] The inventive extruder has at least two support shafts, but
it can also have a substantially larger number of support shafts.
The extruder can thus have for example at least three shafts
parallel to the extruder axis and disposed in a cavity of an
extruder housing along a circle or circular arc at equal
central-angle distance, the extruder housing being provided on the
radially interior and exterior sides of the cavity with concave
circular segments parallel to the extruder axis with the slip-on
elements being guided on said segments. The cavity can also be of
annular configuration. Such an extruder is described e.g. in EP 0
788 867 B.
[0025] The conveying slip-on element is constituted in particular
by a screw element, the working slip-on element e.g. by a
backfeeding screw element with an opposite direction of thread, a
kneader block, a blister or a toothed disk. It is also possible to
provide slip-on elements having a conveying and a working
portion.
[0026] Hereinafter the invention will be explained in more detail
by way of example with reference to the enclosed drawing. Therein
are shown:
[0027] FIG. 1 the transverse profile of two screw elements closely
intermeshing on the circumference in a twin-shaft extruder;
[0028] FIGS. 2 and 3 a side view and front view of a slip-on
element according to a first embodiment;
[0029] FIGS. 4 and 5 a perspective view and front view of a slip-on
element according to a second embodiment; and
[0030] FIGS. 6, 7 and 8 a side view, front view and perspective
view of a slip-on element according to a third embodiment.
[0031] As shown in FIG. 1, two intermeshing slip-on elements 1 have
a transverse or cross-sectional profile area 2 which is limited by
circular arcs A-B, E-F and A-E. The circular arc A-B has a diameter
corresponding to the maximum slip-on element diameter DA, the
circular arc E-F a diameter corresponding to the slip-on element
core diameter Dk, and the circular arc A-E a diameter whose radius
corresponds at most to the center distance Ax of the two combined
slip-on elements 1.
[0032] The slip-on element 1 has an internal toothing 3 engaged by
the support shaft 4 with its external toothing 5. The slip-on
element thus has a free conveying surface 6 that is determined by
the diameter DA and the flight depth. Further, the surface
proportion 7 for the shaft-to-hub connection is needed, which
results from dTA and dTi.
[0033] According to FIGS. 2 and 3, the slip-on element 1 configured
as a screw element likewise has an internal toothing 3 engaged by
the support shaft 4 all around with its external toothing 5. An
involute toothing is provided here. At both ends of the slip-on
element 1 there is an annular reinforcement segment 8, 9 provided
at each end.
[0034] In the embodiment according to FIGS. 4 and 5, the two-start
slip-on element 1 is configured without a shaft-to-hub connection
in the thin area 11, 12 corresponding to the circular arc E-F. That
is, both the slip-on element 1 and the support shaft 4 are of
smooth configuration and fit together all over in the sector
corresponding to the circular arc E-F. The keyways of the involute
toothing 3 thus extend at the ends only into the thick-walled areas
of the slip-on element 1 corresponding to the circular arcs A-E and
A-B. That is, the areas 11 and 12 are not weakened by keyways at
the ends. The toothings 3 have four teeth in each case on both
sides of the thin areas 11, 12, i.e. in the areas opposite the
circular arcs A-B, whereby five splines of the support shaft 4
engage each of the two toothings 3. That is, the torque
transmission takes place with two groups of four teeth and five
splines each, whereby the distance from one group to the other is
greater than that from tooth to tooth or spline to spline of a
group.
[0035] In the embodiment according to FIGS. 6 to 8, the areas of
the single-start slip-on element corresponding to the circular arc
E-F are firstly configured without a shaft-to-hub connection, and
reinforcing rings 13, 14 are moreover provided at the ends, the
reinforcing rings 13, 14 being configured as concentric rings.
Furthermore, the shaft-to-hub connection is configured
concentrically to the axis of the support shaft, as according to
FIGS. 4 and 5. The support shaft 4 is so executed that the smoothly
configured areas of the slip-on element 1 correspond thereto.
* * * * *